In general, a tube has a volume that is variably set depending on whether or not gas is injected, and is used to float an object in the water due to its low specific gravity. Such a tube is used as a buoyant body in a water vehicle, such as a small boat, since it is relatively light and easy to carry.
The tube is generally made of a soft material, such as Polyvinyl Chloride (PVC), polyurethane, or the like. Thus, the tube, which is used as a buoyant body of a water vehicle such as a boat, is vulnerable to damage, such as scratching or tearing, when the water vehicle collides against a sharp object, such as a rock or a coral reef, thereby endangering people in the water vehicle.